Thomas a



(No Model.)

T. A. EDISON.

INGANDESGENT ELECTRIC LAMP.

No. 379,770. Patented Mar. 20, 1888.

WITNESSES 2 INVENTOR 2 C). 18AM? Q fl Jfivw 6 BY 117W? WM ATTORNEYS.

UNTTED STATES PATENT OFFICE.

THOMAS A. EDISON, OF MENLO PARK, NEIV JERSEY, ASSIGNOR TO THE EDISON ELECTRIC LIGHT OOIWIPANY, OF NE\V YORK, N. Y.

INCANDESCENT ELECTRIC LAMP.

SPECIFICATION forming part of Letters Patent No. 379,770, dated March 20, 1888.

Applicationtiled December), lSsl. Serial No. 47,469.

(No model.)

Patented in England October 23, 1878, No. 4,226; in Italy Nrwcinher "21, 1878, No. 4,1151/ 10,156; in Belgium November 30, ISTS, No. 46,567; in Spain February 1,1879, No. 128; in France February 4, 1879, No. 127,341; in Sweden l"ebruar 8. 1557!); in Victoria March 27, 1579, No.

in Norway May 20, 1879; in Canada May 1879, No. 10,031; in Austria-Hungary June 30, 1879, No. 30/864; in Germany March 10, 1880, No. 9,165, and in Russia September 24, 1881.

To all zuhmn it may concern..-

Be it known that I, Tuonms A. EDISON, of Menlo Park, in the county of Middlescx and State of New Jersey, haveinvented a new and useful Improvement in Incandescing Electric Lamps, (OaseNo. 879;) and I do hereby declare that the following is a full and exact descrip tion of the same, reference being had to the accompanying drawings, and to the letters of lo reference marked thereon.

The object I have in view is to produce a lamp which shall have a high resistance with a small radiating-surlace. This I do by employ ing a great length ofcarbon coiled and ar- [5 ranged in such a way that a small radiatingsurface only will be exposed.

The accompanying drawings show two forms of my invention.

In the drawings the coils are drawn apart and enlarged in order that their arrangement will be apparent; bntin practice they are compactly-coiled carbon filaments.

"In Figure 1 three separate spiral carbons, a I) c, are used. The carbons a b are connected to the leading-in wires (Z d, and at their other ends to the ends of the carbon 0, so that the current passes through all three carbons. The large coils of a b are so wound and coiled around the smaller ones of c as to hide the latter and obscure its light.

All the connections are preferably made by electroplating. The best mode of so doing is to first wrap a thin piece of metal about the two ends to be joined, and then electroplate the whole.

In the form shown in Fig. 2 only two carbons, c f, are used, connected together at g, and each having its other end attached to one of lilhe-leading-in wires a a, h being simply a support. The coils off are placed above those of (1, so as to obscure them.

It is evident that many other forms of coiled and spiral carbons could be used without departing from the principle 01' myinvention.

The excessive length of carbon gives the proper amount of resistance, while the manner in which the carbons are coiled decreases the radiating-Snrlace.

What I claim is 1. In an incamlescing electric lamp, thecombination of two carbons,placed one within the other, for reducing their effective radiatingsurface and increasing the electrical resistance, substantially as set forth.

2. In an incandcscing electric lamp, the combination of two or more spiral carbon conductors, connected in series, the coils of one covering and partially hiding those of the others, substantially as and for the purpose set forth.

This specification signed and witnessed this 5th day 01' December, 1881.

THOMAS A. EDISON.

'Witnesscs:

1i. W. SEELY, WM. H. Mnanowonor'r. 

